1. Field of the Invention
The invention concerns a device for rounding the ends of the fibres of brushes, in particular fibres which are made of synthetic material, which device contains a first support which can be moved in a direction in relation to a brush; a second support which is mounted, rotatable around an axis which is at right angles to said direction, on the support; means to rotate this second support; a grinding surface which is mounted in a moveable manner on the second support and against which the fibres are provided; and means to move this grinding surface.
2. Discussion of the Prior Art
During the manufacturing of the brushes, after the insertion, the free ends of the brushes are shaved off so as to smooth away the unevennesses which have arisen during the insertion of the fibres. As a result of this shaving, sharp edges are created at the fibre ends, which cannot be tolerated for certain brushes.
This is for example the case for tooth brushes, where the sharp edges could hurt the gums, or for hair brushes, where the sharp edges could hurt the scalp.
EP-A-0 019 944 describes a device for rounding the ends of the fibres of the above-mentioned type. In this device, the grinding surface consists of a disc which is equipped with a suitable abrasive and/or a suitable moulded pattern and which is mounted on the second support in a rotatable manner around a shaft which is parallel to, but eccentric to the axis around which this second support can in turn rotate in relation to the first support. The whole device (first support, disk, second support can be shifted back and forth.
The linear speed of a point of such a disk, during the rotation, is higher as this point is situated further from the axis of rotation. This implies that when a brush is put into contact with the disk, the fibres make contact with points which have different peripheral velocities, so that the fibres are ground and rounded at different grinding speeds. This uneven grinding effect is disadvantageous for the quality of the brush. Moreover, the rotating disc always moves in the same sense, so that also the direction of grinding is always the same. Hence, with such an arrangement, two grinding units, whose discs are driven in the opposite sense, must be provided for proper grinding, which is a costly solution.
In order to remedy these disadvantages, it has already been suggested to replace the disc by a grinding belt running over horizontal rollers, whereby the brushes are put against a topmost flat part of the grinding belt and whereby all points of this grinding surface move at the same speed. In order to change the grinding direction, the entire belt is rotated around a vertical shaft, but the advantage of the equal speed is consequently lost. The belt must be as wide as the length of the brush, since the latter must be able to rest entirely on the grinding surface. Due to the rotation of the belt, the points of the belt will make a combined, total movement which is larger as they are situated further away from the axis of the vertical shaft. Given the large width of the belt, the differences in speed can be significant.
In both these known devices, the entire brush surface, or in the case of a tooth brush the entire surface of the brush head, makes contact with the grinding surface so that, apart from the above-mentioned disadvantages, the different fibres make contact with other points of the grinding surface at the same time, so that even more differences may be created during the grinding process to which these fibres are subjected.